The present invention relates to engines useful in model airplanes and like and particularly to two-stroke engines for model airplane and similar applications.
The invention is especially suitable for use in a model airplane engine or like engine to facilitate starting the engine, especially in a cold temperature environment (e.g. under 10xc2x0 C.) and to enable the use of fuel that is heavier and less combustible than fuels conventionally specified for use in such an engine.
Briefly, the invention may be carried out by providing an engine with a heated backplate assembly. An engine embodying the invention may be provided by either replacing the standard backplate in said engines with an electrically,heated backplate assembly, or retrofitting an existing backplate with the heater.
Model airplane engines are notoriously hard to start in cold weather. Furthermore, such engines require for their operation special fuels, such as nitromethane-methanol mixtures, which are expensive and hazardous to use because of their high volatility.
In accordance with the invention, it was discovered when a standard engine backplate is replaced with a backplate that is heated, as by incorporating therein a resistive, electrically heated element, an improved engine is provided which is easier to start and does not require special fuel as is the case for the standard engine. During start, the heating element is temporarily energized from a battery, heating the engine to a temperature sufficient to vaporize the fuel prior to its entry into the combustion cylinder. Because no liquid fuel enters the cylinder, crankcase and cylinder flooding are prevented. Under these conditions the engine easily starts in cold, ambient temperatures. The improved engine can use heavier, less volatile fuels, e.g. Jet xe2x80x9cAxe2x80x9d fuel. After the engine starts the heating element is disconnected from said battery.
Related technology to this invention, includes C. W. Mc Cutchen in U.S. Pat. No. 4,002,882 which describes a heating circuit for model airplane engines designed, unlike the present invention, to heat the ignition glow plug of the engine. Additionally, operation and construction of model airplane engines is described in a book entitled xe2x80x9c2-Stroke Glow Engines for R/C Aircraftxe2x80x9d, V.1, Model Airplane News, 1994, Air Age Inc., p.p. 11,12, and 31-34.
A further feature of this invention is to provide a method for fabricating improved engines by providing a selection of backplate assemblies in configurations and sizes that facilitate the installation a said backplate assemblies in a majority of models and makes of model airplane engines.